2006A&A...457..995V


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.08CET00:20:17

2006A&A...457..995V - Astronomy and Astrophysics, volume 457, 995-1001 (2006/10-3)

Does the oxygen-sodium anticorrelation in globular clusters require a lowering of the 23Na(p,α)20Ne reaction rate?

VENTURA P. and D'ANTONA F.

Abstract (from CDS):

The chemical content of the ejecta of Asymptotic Giant Branch stars (AGBs) is important to understand whether intermediate mass stars played a role in the ``self-enrichment scenario'', to explain the chemical anomalies observed among Globular Clusters stars. One difficulty of this model is that it is not fully consistent with the observed oxygen-sodium anticorrelation. We look for the combinations of the input-physics parameters by which the yields of massive AGBs are sodium-rich and oxygen-poor. Many evolutions from the early evolutionary phases until the mass of the envelope drops below ∼0.5M are calculated for a 5MZ=0.001 model for various assumptions concerning the extra mixing from the bottom of the envelope and the relevant cross sections involving sodium. A modest amount of extra mixing from the bottom of the surface convective zone leads to ejecta that are moderately sodium rich and oxygen depleted. A different but appealing modelization allows us to reproduce the observations of stars with a lower oxygen content: extra mixing is not included, but the cross sections of the reaction 23Na(p, α)20Ne must be a factor of ∼4 lower than the recommended values. If the initial neon content of the star is not solar-scaled but enhanced as the other α elements by a factor ∼2, the afore mentioned cross section must be lessened by only a factor ∼2.

Abstract Copyright:

Journal keyword(s): stars: abundances - stars: AGB and post-AGB - stars: evolution

Simbad objects: 7

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Number of rows : 7

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NGC 2808 GlC 09 12 03.10 -64 51 48.6   7.77 5.69     ~ 1279 0
2 M 3 GlC 13 42 11.62 +28 22 38.2     6.39     ~ 2298 0
3 M 5 GlC 15 18 33.22 +02 04 51.7   7.34 5.95     ~ 1806 0
4 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1704 0
5 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 2036 0
6 NGC 6397 GlC 17 40 42.09 -53 40 27.6   7.39 5.17     ~ 1822 1
7 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1835 0

    Equat.    Gal    SGal    Ecl

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2021.03.08-00:20:17

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